The present invention relates to breathing equipment designed to supply the wearer with breathing gas under a pressure greater than ambient pressure, the equipment being of the type comprising a face mask having a rigid shell provided with means for fastening to head straps, a coupling for feeding breathing gas under pressure, and a face-cover of elastomer material terminated by at least one lip for bearing against the face.
Very often, particularly during military missions, a mask must be worn permanently even though it is used only exceptionally or only during a short fraction of a mission. This gives rise to requirements that, until now, have been to a large extent contradictory. The mask must be continuously in place in such a manner that immediately on it being fed with breathing gas under pressure, leaks are avoided along the zone of contact between the mask and the skin. Attempts have been made to achieve this result by providing the face-cover with an internal lip that tends to be pressed against the face by pressure inside the mask. However, for that to work, it is necessary for there to be no initial leakage preventing the pressure from building up significantly. To limit this risk, the straps must be tight enough to press the mask against the face. However, under such circumstances, the zone where the lip presses against the face quickly becomes painful. In addition, the difference in hardness between the various zones of the face, the lack of an accurate fit between the mask and various different possible wearers, and the risk of the mask being put into place inaccurately, all combine to ensure that the danger of leaks is not eliminated completely.
To reduce discomfort, proposals have already been made to interpose flexible folds between the front portion of the mask which is fitted with the strap and a rear portion that bears against the face, and in particular against the bridge of the nose, which folds make it possible to improve contact for a given application force due to the strap (U.S. Pat. No. 2,706,983). However, although that solution is acceptable when feeding air through a filter which does not give rise to an increase in pressure, it cannot guarantee initial airtight application of a mask that is intended, under some circumstances, to receive a breathing gas under pressure. Proposals have also been made (U.S. Pat. No. 4,069,516) for a breathing mask designed to be connected to a demand regulator and including a coupling front portion and a rear portion constituting a sealing lip, which portions are connected to each other by a flexible fold constituting a hinge. Like the preceding solution, that solution is not entirely satisfactory. If the mask is not accurately fitted to the face, then the lip can lift off locally, thus giving rise to leaks when gas is fed to the mask.